Lili Mu

Disequilibrium of T helper type 1, 2 and 17 cells and regulatory T cells during the development of experimental autoimmune myasthenia gravis

Experimental autoimmune myasthenia gravis (EAMG), an animal model of myasthenia gravis (MG), is a rare organ‐specific autoimmune disease targeting the autoantigen nicotinic acetylcholine receptor (AChR). We show here that the balance of T helper type 1 (Th1), Th2, Th17 and regulatory T (Treg) subsets of CD4+ helper T cells were redistributed during the development of EAMG and that the interleukin‐17 (IL‐17) cytokine is involved in this disease. The ratio of Th17 cells changed most notably with disease progression accompanied by an up‐regulated level of IL‐17. Moreover, the proliferative ability of AChR peptide‐specific T cells and the anti‐AChR antibody‐secreting cells increased when stimulated by IL‐17 in vitro. These findings suggested that the disequilibrium of the CD4+ helper T‐cell subsets could promote the development of EAMG, and the pathogenic mechanism by which Th17 cells drives autoimmune responses by secreting cytokine IL‐17 provides a new target for myasthenia gravis therapy.

IL-17 potentiates neuronal injury induced by oxygen–glucose deprivation and affects neuronal IL-17 receptor expression

Interleukin-17 (IL-17) is active in a variety of brain injuries, including ischemia. The objective of this study was to test the hypothesis that IL-17 potentiates neuronal injury after stroke. Increased expression of IL-17 and IL-17 receptor (IL-17R) in serum and cortex was evaluated by ELISA, RT-PCR and immunohistochemistry. In the in vitro model of oxygen-glucose deprivation (OGD), IL-17 showed a dose-dependent effect in promoting neuronal injury through IL-17-IL-17R combination which can be blocked by IL-17R/Fc chimera. Our results demonstrated the up-regulation of IL-17 and IL-17R following permanent middle cerebral artery occlusion and suggested that they contributed to stroke outcome.

BM stromal cells ameliorate experimental autoimmune myasthenia gravis by altering the balance of Th cells through the secretion of IDO

In addition to their capacity to differentiate, BM stromal cells (BMSC) have immunosuppressive qualities that make them strong candidates for use in cell therapy against human autoimmune diseases. We studied the immunoregulatory activities of BMSC on experimental autoimmune myasthenia gravis (EAMG) in vitro and in vivo. Intravenous administration of syngenic BMSC to EAMG‐model rats on the day of their second immunization was effective in ameliorating the pathological features of the disease. In vitro, the proliferative ability of T cells or B cells from EAMG rats was inhibited when they were cocultured with BMSC at proper ratios. This inhibitory effect was at least partially dependent on the secretion of IDO. We also determined that the development of EAMG is accompanied by an imbalance among the Th1, Th2, Th17, and Treg cell subsets, and that this can be corrected by the administration of BMSC, which leads to an increase of Th2 (IL‐4) and Treg (Foxp3) cells, and a reduction of Th1 (IFN‐γ) and Th17 (IL‐17) cells, through an IDO‐dependent mechanism. These results provide further insights into the pathogenesis of MG, EAMG, and other immune‐mediated diseases, and support a potential role for BMSC in their treatment.

Simulated microgravity promotes cellular senescence via oxidant stress in rat PC12 cells

Microgravity has a unique effect on biological organisms. Organs exposed to microgravity display cellular senescence, a change that resembles the aging process. To directly investigate the influence of simulated microgravity on neuronal original rat PC12 cells, we used a rotary cell culture system that simulates the microgravity environment on the earth. We found that simulated microgravity induced partial G1 phase arrest, upregulated senescence-associated beta-galactosidase (SA-beta-gal) activity, and activated both p53 and p16 protein pathways linked to cell senescence. The amount of reactive oxygen species (ROS) was also increased. The activity of intracellular antioxidant enzymes, such as superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT), was all significantly increased at 12h after the microgravity onset, yet decreased at 96h. Furthermore, concomitant block of ROS by the antioxidant N-acetylcysteine significantly inhibited the microgravity-induced upregulation of SA-beta-gal activity. These results suggest that exposure to simulated microgravity induces cellular senescence in PC12 cells via an increased oxidant stress.

Activation of the adenosine A2A receptor attenuates experimental autoimmune myasthenia gravis severity

The adenosine A2A receptor (A2AR) is the major cellular adenosine receptor commonly associated with immunosuppression. Here, we investigated whether A2AR activation holds the potential for impacting the severity of experimental autoimmune myasthenia gravis (EAMG) induced following immunization of Lewis rats with the acetylcholine receptor (AChR) R97–116 peptide. This report demonstrates reduced A2AR expression by both T cells and B cells residing in spleen and lymph nodes following EAMG induction. A2AR stimulation inhibited anti‐AChR antibody production and proliferation of AChR‐specific lymphocytes in vitro. Inhibition was blocked with the A2AR antagonists or protein kinase A inhibitor. We also determined that the development of EAMG was accompanied by a T‐helper cell imbalance that could be restored following A2AR stimulation that resulted in increased Treg cell levels and a reduction in Th1‐, Th2‐, and Th17‐cell subtypes. An EAMG‐preventive treatment regimen was established that consisted of (2‐(p‐(2‐carbonylethyl)phenylethylamino)‐5‐N‐ethylcarboxamidoadenosine) (CGS21680; A2AR agonist) administration 1 day prior to EAMG induction. Administration of CGS21680 29 days post EAMG induction (therapeutic treatment) also ameliorated disease severity. We conclude that A2AR agonists may represent a new class of compounds that can be developed for use in the treatment of myasthenia gravis or other T‐cell‐ and B‐cell‐mediated autoimmune diseases.

The effect of electroacupuncture on T cell responses in rats with experimental autoimmune encephalitis

Successive electroacupuncture (EA) stimulation on Zusanli ST36 acupoints of rats with experimental autoimmune encephalitis (EAE), which is an inflammatory disease mediated by autoreactive T cells, relieved disease severity, inhibited specific T cell proliferation and rebuilt the CD4+ T cell subset balance. In addition, EA-treated rats had significantly higher ACTH concentrations in vivo compared to untreated EAE rats. These results indicated that EA stimulation could relieve the severity of EAE by restoring balance to the Th1/Th2/Th17/Treg Th cell subset responses by stimulating the hypothalamus to increase ACTH secretion.

All-trans-retinoic acid ameliorates experimental allergic encephalomyelitis by affecting dendritic cell and monocyte development.

Experimental allergic encephalomyelitis (EAE) can be induced in animal models by injecting the MOG35–55 peptide subcutaneously. Dendritic cells (DCs) that are located at the immunization site phagocytose the MOG35–55 peptide. These DCs mature and migrate into the nearest draining lymph nodes (dLNs), then present antigen, resulting in the activation of naive T cells. T helper type 1 (Th1) and Th17 cells are the primary cells involved in EAE progression. All‐trans‐retinoic acid (AT‐RA) has been shown to have beneficial effects on EAE progression; however, whether AT‐RA influences DC maturation or mediates other functions is unclear. In the present study, we showed that AT‐RA led to the down‐regulation of MHC class II, CD80 (B7‐1) and CD86 (B7‐2) expressed on the surface of DCs that were isolated from dLNs or spleen 3 days post‐immunization in an EAE model. Changes to DC function influenced Th1/Th17 subset polarization. Furthermore, the number of CD44+ monocytes (which might trigger EAE progression) was also significantly decreased in dLNs, spleen, subarachnoid space and the spinal cord parenchyma after AT‐RA treatment. These findings are the first to demonstrate that AT‐RA impairs the antigen‐presenting capacity of DCs, leading to down‐regulation of pathogenic Th1 and Th17 inflammatory cell responses and reducing EAE severity.

Activation of the receptor for advanced glycation end products (RAGE) exacerbates experimental autoimmune myasthenia gravis symptoms

RAGE belongs to immunoglobulin superfamily and serves as a ligand for various immunoregulatory molecules including S100B that has been demonstrated important to T cell mediated autoimmune diseases. In this context, we hypothesized that RAGE could also impact B cell mediated, T cell-dependent autoimmune diseases. This was tested using myasthenia gravis (MG) animal model, EAMG. We show that expression of both RAGE and S100B are increased during EAMG and the interaction between RAGE and S100B affected the Th1/Th2/Th17/Treg cell equilibrium, up-regulate AChR-specific T cell proliferation. Furthermore, addition of S100B in vitro stimulated splenocyte activity linked to COX-2 up-regulation. NS-398, a selective COX-2 inhibitor, effectively diminished S100B mediated activity of AChR-specific antibody secreting splenocytes. These findings suggested that a reciprocal relationship between RAGE and S100B promoted the development of EAMG, highlighting the importance of understanding the mechanisms of EAMG disease as a means of developing new therapies for the treatment of MG.

ATRA alters humoral responses associated with amelioration of EAMG symptoms by balancing Tfh/Tfr helper cell profiles

All-trans retinoic acid (ATRA) is a vitamin A metabolite with diverse immunomodulatory actions used therapeutically in the treatment of some autoimmune diseases. However, the effects that ATRA may have on diminishing myasthenia gravis (MG) symptoms remain undefined. This study investigated the effect of ATRA on experimental autoimmune myasthenia gravis (EAMG) in vivo and in vitro. Data presented in this study demonstrated that intraperitoneal injection of ATRA ameliorated EAMG pathology in rats associated with reduced total anti-acetylcholine receptor (AChR) serum IgG levels. We observed that EAMG development was accompanied by an increase in follicular helper T cells (Tfh, defined as CD4(+)CXCR5(+)ICOS(high)) and a decrease of follicular regulatory T cells (Tfr, defined as CD4(+)Foxp3(+)CXCR5(+)ICOS(median)) and that the Tfh:Tfr ratio was altered following ATRA administration. In addition, ATRA treatment restored the Th1/Th2/Th17/Treg balance. In vitro, ATRA inhibited AChR-specific cell proliferation and eliciting apoptosis in these cells without affecting the cell cycle. ATRA also altered the Th distribution in animals presenting with EAMG resulting in a reduction in Th1/Th17/Tfh cells and increasing the number of Th2/Treg/Tfr cell types. These results suggested that ATRA reduced EAMG severity by regulating Th cell profiles thereby providing new insights into the development of novel MG (or related) therapies.

Characterization of the interaction between astrocytes and encephalitogenic lymphocytes during the development of experimental autoimmune encephalitomyelitis (EAE) in mice

The nature of pathogenic mechanisms associated with the development of multiple sclerosis (MS) have long been debated. However, limited research was conducted to define the interplay between infiltrating lymphocytes and resident cells of the central nervous system (CNS). Data presented in this report describe a novel role for astrocyte‐mediated alterations to myelin oligodendrocyte glycoprotein (MOG)35–55‐specific lymphocyte responses, elicited during the development of experimental autoimmune encephalitomyelitis (EAE). In‐vitro studies demonstrated that astrocytes inhibited the proliferation and interferon (IFN)‐γ, interleukin (IL)‐4, IL‐17 and transforming growth factor (TGF)‐β secretion levels of MOG35–55‐specific lymphocytes, an effect that could be ameliorated by astrocyte IL‐27 neutralization. However, when astrocytes were pretreated with IFN‐γ, they could promote the proliferation and secretion levels of MOG35–55‐specific lymphocytes, coinciding with apparent expression of major histocompatibility complex (MHC)‐II on astrocytes themselves. Quantitative polymerase chain reaction (qPCR) demonstrated that production of IL‐27 in the spinal cord was at its highest during the initial phases. Conversely, production of IFN‐γ in the spinal cord was highest during the peak phase. Quantitative analysis of MHC‐II expression in the spinal cord showed that there was a positive correlation between MHC‐II expression and IFN‐γ production. In addition, astrocyte MHC‐II expression levels correlated positively with IFN‐γ production in the spinal cord. These findings suggested that astrocytes might function as both inhibitors and promoters of EAE. Astrocytes prevented MOG35–55‐specific lymphocyte function by secreting IL‐27 during the initial phases of EAE. Then, in the presence of higher IFN‐γ levels in the spinal cord, astrocytes were converted into antigen‐presenting cells. This conversion might promote the progression of pathological damage and result in a peak of EAE severity.